Original Articles Functional Plasticity of the Motor Cortical Structures Demonstrated by Navigated TMS in Two Patients with Epilepsy Jyrki P. Mäkelä a, * , Anne-Mari Vitikainen a, b, c , Pantelis Lioumis a , Ritva Paetau a, d, e , Eero Ahtola c , Linda Kuusela b, c , Leena Valanne c , Göran Blomstedt f , Eija Gaily d a BioMag Laboratory, HUSLAB, Hospital District of Helsinki and Uusimaa, Helsinki University Central Hospital, P.O. Box 340, FI-00029 HUS, Helsinki, Finland b University of Helsinki, Department of Physics, P.O. Box 64, FI-00014 Helsinki, Helsinki, Finland c HUS Helsinki Medical Imaging Center, Hospital District of Helsinki and Uusimaa, Helsinki University Central Hospital, P.O. Box 340, FI-00029 HUS, Helsinki, Finland d Helsinki University Central Hospital, Pediatric Neurology, Epilepsy Unit, P.O. Box 280, FI-00029 HUS, Helsinki, Finland e Department of Clinical Neurophysiology, HUSLAB, Hospital District of Helsinki and Uusimaa, Helsinki University Central Hospital, P.O. Box 280, FI-00029 HUS, Helsinki, Finland f Department of Neurosurgery, Hospital District of Helsinki and Uusimaa, Helsinki University Central Hospital, P.O. Box 266, FI-00029 HUS, Helsinki, Finland article info Article history: Received 18 January 2012 Received in revised form 26 March 2012 Accepted 28 April 2012 Available online 1 June 2012 Keywords: Epilepsy surgery FCD Premotor cortex MEG fMRI Tractography abstract Background: Recently, navigated transcranial magnetic stimulation (nTMS) has been suggested to be useful in preoperative functional localization of motor cortex in patients having tumors close to the somatomotor cortex. Resection of tumors in anatomically predicted eloquent areas without adverse effects have emphasized functional plasticity elicited by intracranial pathology. Objective: To describe functional plasticity of motor cortex indicated by nTMS in two patients with epilepsy. Methods: nTMS, functional MRI (fMRI), diffusion-tensor (DT)-tractography and magnetoencephalography (MEG) were utilized to preoperatively localize motor cortical areas in the workup for epilepsy surgery. The localizations were compared with each other, with the cortical anatomical landmarks, and in one patient with invasive electrical cortical stimulation (ECS). Results: In two out of 19 studied patients, nTMS identified motor cortical sites that differed from those indicated by anatomical landmarks. In one patient, nTMS activated preferentially premotor cortex rather than pathways originating from the precentral gyrus. MEG and fMRI localizations conformed with nTMS whereas ECS localized finger motor function into the precentral gyrus. Resection of the area producing motor responses in biphasic nTMS did not produce a motor deficit. In the other patient, nTMS indicated abnormal ipsilateral hand motor cortex localization and confirmed the functionality of aberrant motor cortical representations of the left foot also indicated by fMRI and DT-tractography. Conclusion: nTMS may reveal the functional plasticity and shifts of motor cortical function. Epileptic foci may modify cortical inhibition and the nTMS results. Therefore, in some patients with epilepsy, the nTMS results need to be interpreted with caution with regard to surgical planning. Ó 2013 Elsevier Inc. All rights reserved. Introduction Noninvasive transcranial magnetic stimulation (TMS) utilizes fast magnetic pulses to modify cortical activity. It has become an important tool in the evaluation of the human central motor pathways [1]. Navigated TMS (nTMS) displays dynamic estimate of the stimulus-induced electric field on the patient’s individual 3-D brain MRI reconstruction, and enables selection of localized stim- ulation targets from it. Recently, nTMS has been suggested to be a useful tool in preoperative localization of motor cortex in precentral gyrus, harboring Brodmann area 4 considered as the primary motor cortex, in patients with tumors in close vicinity of somatomotor cortex. In prospective series of altogether 42 patients, comparison of the preoperative nTMS and intraoperative direct cortical stimulation (DCS) localization of hand motor representa- tion in the precentral gyrus has given differences of 4e10 mm without exceptions [2e4]. nTMS was found to be clearly more accurate than fMRI [2,4]. nTMS provides useful information also in preoperative planning of epilepsy surgery [5,6]. Pantelis Lioumis has received grants from HUS-EVO funding and from the SalWe Research Program for Mind and Body (Tekes e the Finnish Funding Agency for Technology and Innovation grant 1104/10). The authors report no conflicts of interest. * Corresponding author. Tel.: þ358 50 4279051; fax: þ358 9 47175781. E-mail address: jyrki.makela@hus.fi (J.P. Mäkelä). Contents lists available at SciVerse ScienceDirect Brain Stimulation journal homepage: www.brainstimjrnl.com 1935-861X/$ e see front matter Ó 2013 Elsevier Inc. All rights reserved. doi:10.1016/j.brs.2012.04.012 Brain Stimulation 6 (2013) 286e291